More than seven years after its debut, Windows NT4 remains the hosting Operating System of choice for a surprising number of big brand web sites. But with Windows NT4 officially retired and Microsoft planning to discontinue security patches and support at year-end, even die hard enterprises still running NT4 will presumably switch eventually.

One which seems to have started is auction giant eBay, which has recently begun shifting some of its web infrastructure from Windows NT4 to Windows Server 2003. WinNT4 continues to power much of eBay's main site, which handled 971 million auction listings in 2003.

eBay is hardly alone, as other major enterprise companies still running their public web sites on Windows NT4 include Gateway, The Bank of New York, Heinz, Hershey Foods, Ikea, Kroger and Diebold. In the UK, 10 members of the FTSE 100 run on NT4/98, among them the retailer Next Group PLC, and LLoyds TSB.

At present Microsoft is the only member of the Fortune 100 hosting its main public site on Windows 2003 Server, while Tesco Stores is the lone FTSE 100 company on Win2003. Recent data from our SSL Survey suggests that many e-commerce operations previously on WinNT4 are now shifting to to Windows 2003 Server.

The bulk of machines serving pages.ebay.com continue to run on Windows NT4. The auctioneer didn't completely forego Windows 2000, as many of its specialty sites run on Win2K, while some overseas eBay editions (including Hong Kong and Singapore) are served on Linux.

Netcraft monitors over 23K hostnames for the top 1.5K Enterprises (Fortune 1K, FT European 500, FT Asia Pacific, FT Japan, FT Eastern Europe) on a monthly basis, providing details of web technology. Contact us for details of the commercial dataset.